drivers/leds/leds-lp5523.c: adjust delays and add comments to them

Delays were little bit too long.  Adjust delay times and add some comments
to them.

Signed-off-by: Samu Onkalo <samu.p.onkalo@nokia.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 17 insertions, 14 deletions

diff --git a/drivers/leds/leds-lp5523.c b/drivers/leds/leds-lp5523.c
index 053e1f8b6c0b..4248d78cec37 100644
--- a/drivers/leds/leds-lp5523.c
+++ b/drivers/leds/leds-lp5523.c
@@ -205,11 +205,14 @@ static int lp5523_configure(struct i2c_client *client)
 
         lp5523_write(client, LP5523_REG_RESET, 0xff);
 
-        usleep_range(10000, 100000);
+        usleep_range(10000, 20000); /*
+                                     * Exact value is not available. 10 - 20ms
+                                     * appears to be enough for reset.
+                                     */
 
         ret |= lp5523_write(client, LP5523_REG_ENABLE, LP5523_ENABLE);
-        /* Chip startup time after reset is 500 us */
-        usleep_range(1000, 10000);
+        /* Chip startup time is 500 us, 1 - 2 ms gives some margin */
+        usleep_range(1000, 2000);
 
         ret |= lp5523_write(client, LP5523_REG_CONFIG,
                             LP5523_AUTO_INC | LP5523_PWR_SAVE |
@@ -246,8 +249,8 @@ static int lp5523_configure(struct i2c_client *client)
                 return -1;
         }
 
-        /* Wait 3ms and check the engine status */
-        usleep_range(3000, 20000);
+        /* Let the programs run for couple of ms and check the engine status */
+        usleep_range(3000, 6000);
         lp5523_read(client, LP5523_REG_STATUS, &status);
         status &= LP5523_ENG_STATUS_MASK;
 
@@ -452,10 +455,10 @@ static ssize_t lp5523_selftest(struct device *dev,
         /* Measure VDD (i.e. VBAT) first (channel 16 corresponds to VDD) */
         lp5523_write(chip->client, LP5523_REG_LED_TEST_CTRL,
                                     LP5523_EN_LEDTEST | 16);
-        usleep_range(3000, 10000);
+        usleep_range(3000, 6000); /* ADC conversion time is typically 2.7 ms */
         ret = lp5523_read(chip->client, LP5523_REG_STATUS, &status);
         if (!(status & LP5523_LEDTEST_DONE))
-                usleep_range(3000, 10000);
+                usleep_range(3000, 6000); /* Was not ready. Wait little bit */
 
         ret |= lp5523_read(chip->client, LP5523_REG_LED_TEST_ADC, &vdd);
         vdd--;  /* There may be some fluctuation in measurement */
@@ -471,16 +474,16 @@ static ssize_t lp5523_selftest(struct device *dev,
                         chip->pdata->led_config[i].led_current);
 
                 lp5523_write(chip->client, LP5523_REG_LED_PWM_BASE + i, 0xff);
-                /* let current stabilize 2ms before measurements start */
-                usleep_range(2000, 10000);
+                /* let current stabilize 2 - 4ms before measurements start */
+                usleep_range(2000, 4000);
                 lp5523_write(chip->client,
                              LP5523_REG_LED_TEST_CTRL,
                              LP5523_EN_LEDTEST | i);
-                /* ledtest takes 2.7ms */
-                usleep_range(3000, 10000);
+                /* ADC conversion time is 2.7 ms typically */
+                usleep_range(3000, 6000);
                 ret = lp5523_read(chip->client, LP5523_REG_STATUS, &status);
                 if (!(status & LP5523_LEDTEST_DONE))
-                        usleep_range(3000, 10000);
+                        usleep_range(3000, 6000);/* Was not ready. Wait. */
                 ret |= lp5523_read(chip->client, LP5523_REG_LED_TEST_ADC, &adc);
 
                 if (adc >= vdd || adc < LP5523_ADC_SHORTCIRC_LIM)
@@ -933,9 +936,9 @@ static int lp5523_probe(struct i2c_client *client,
 
         if (pdata->enable) {
                 pdata->enable(0);
-                usleep_range(1000, 10000);
+                usleep_range(1000, 2000); /* Keep enable down at least 1ms */
                 pdata->enable(1);
-                usleep_range(1000, 10000); /* Spec says min 500us */
+                usleep_range(1000, 2000); /* 500us abs min. */
         }
 
         ret = lp5523_detect(client);